Many fuel consuming systems are catalytically driven. Such systems include fuel reformers for instance for the oxidation or partial oxidation of fuels.
Other catalytic systems which come into contact with fuels or with the by-products of fuel consumption (in particular fuel combustion) include the exhaust aftertreatment systems of automotive vehicles.
In such systems, the content of the fuel may influence catalyst performance, particularly if the fuel contains agents capable of acting, in the context, as catalyst “poisons”. In particular in the case of an exhaust aftertreatment system, however, the fuel and fuel by-products passing through it may contain all manner of additives which are included in the fuel for purposes unrelated to the operation of the exhaust system.
For example, fuel compositions for use in typical current diesel (compression ignition) engines tend to include one or more additives to enhance their performance and properties. Such additives include antifoaming agents to reduce foaming during engine refueling. The antifoaming agents typically preferred for use in diesel fuels are silicone based.
Silicon, which may be contained in fuel additives, can cause degradation of catalyst efficiency when present in the fuel feed to a catalytically driven fuel processor. It might also therefore be expected to compromise, to at least a degree, catalyst efficiency in other catalytically driven systems, including the exhaust aftertreatment systems of diesel vehicles running on similarly additivated fuels.
Moreover, silicon deposits have also been found in the deposits which accumulate in the fuel injectors of diesel engines. High levels of such deposits can impair fuel atomization and combustion and hence overall engine efficiency.